Difference Between GMT and IST

22-11-2024

06:30 AM

Understand the Difference Between GMT and IMT in the article below. Learn about the number of time zones in India. A must-read for UPSC 2024 aspirants, with tips from Vajiram and Ravi.

GMT is the Greenwich Mean Time which is the unified time zone adopted by most of the English countries which are measured in London at midnight, whereas IMT is the Indian Standard Time which is 5 hours 30 minutes ahead of GMT. This time standard is essential for various activities, including legal, social, and business purposes. There are numerous time zones across the globe, with each country or region selecting the time zone that best fits their geographical position and needs.

Understanding the Difference Between GMT and IMT is crucial for UPSC aspirants, as it is a significant topic in the Geography section. This topic features majorly in both the Mains General Studies Paper-1 and the UPSC Prelims Syllabus 2024.

Difference Between GMT and IMT

A time zone is a region on Earth where a consistent standard time is followed. While countries have the freedom to choose a time zone within their borders, two time zones are renowned worldwide: Indian Standard Time (IST) and Greenwich Mean Time (GMT).

Difference Between GMT and IMT
GMT (Greenwich Mean Time)	IST (Indian Standard Time)
The Greenwich Mean Time was created by the Royal Observatory in 1675 for assistance navigators at sea.	The Indian Standard Time was established as the official time zone of India upon its independence on August 15th, 1947
When calculating GMT it is considered equivalent to UT1 (the modern form of mean solar time at 0° longitude), but this meaning can differ from UTC by up to 0.9 seconds.	The IST is calculated on the basis of a clock tower in Mirzapur (with coordinates 25.15° North Latitude and 82.58° East longitude).
Because of Earth’s uneven angular velocity in its elliptical orbit, GMT is rarely the exact moment the Sun crosses the Greenwich meridian	The Time and Frequency Standards Laboratory at the National Physical Laboratory in New Delhi generates official time signals for both commercial and official purposes. These signals are derived from atomic clocks and are synchronised with the global network of clocks.
Time zones are determined by a combination of legal, political, and geographical factors, meaning they do not always align perfectly with meridian lines. This also applies to Greenwich Mean Time (GMT), as discrepancies arise between the legal and geographical definitions of GMT.	India's single time zone, IST, doesn’t suit its vast geography. The country’s east-west stretch of 2,933 kilometres causes the sun to rise and set nearly two hours earlier in the east than in the west. To address this, the government has recently considered introducing multiple time zones.
The term Greenwich Mean Time is used commonly in the United Kingdom and in the Commonwealth of Nations such as Australia, New Zealand and many other countries of the Eastern Hemisphere	Indian Standard Time is used in India and Sri Lanka but it takes references from the UTC (Universal Time Coordinate). The UTC has been developed as a successor to the Greenwich Mean Time

Facts About Indian Standard Time

The Council of Scientific & Industrial Research – National Physical Laboratory (CSIR-NPL), which is responsible for maintaining Indian Standard Time (IST), has put forward a proposal suggesting the adoption of two time zones in India.
The proposal includes IST I (UTC+5:30) for the entire country and IST II (UTC+6:30) specifically for the North-Eastern regions.
This recommendation comes in response to the early sunrise in the easternmost parts of India, where the country’s wide longitudinal span results in significant daylight hours being lost.
The Indian government has not supported this proposal, mentioning potential challenges and complexities involved in implementing two separate time zones.

Difference Between GMT and IMT FAQs

Q1. What is the time difference between GMT and IST?

Ans. The Indian Standard Time (IST) is ahead of the Greenwich Mean Time (GMT) by 5 hours 30 mins.

Q2. What are the countries in the IST time zone?

Ans. IST (Indian Standard Time) zone are followed in India and Sri Lanka.

Q3. What is the Standard Meridian of India?

Ans. The 82.5 degree longitude is considered as the standard meridian of India.

Q4. Which states cross the Indian Standard Time line?

Ans. The Indian Standard Time line passes through the states of Uttar Pradesh, Madhya Pradesh, Chhattisgarh, Orissa and Andhra Pradesh.